Techniques for measuring a location of UE

ABSTRACT

The present invention provides a method for measuring a location. The method comprises: receiving, by a User Equipment (UE) and from a serving cell, information on a bandwidth allocated for a positioning reference signal (PRS); receiving, by the User Equipment (UE) and from at least one or more neighbor cells, information on a bandwidth allocated for a PRS; determining whether there is a difference between the bandwidths; and measuring, by the UE and based on a result of the determination a timing difference between PRSs transmitted from the serving cell and the at least one or more neighbor cells.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/732,539, filed on Jun. 5, 2015, now U.S. Pat. No. 9,374,728, which isa continuation of U.S. application Ser. No. 13/992,918, filed on Jun.10, 2013, now U.S. Pat. No. 9,084,127, which is the National Stagefiling under 35 U.S.C. 371 of International Application No.PCT/KR2011/009493, filed on Dec. 8, 2011, which claims the benefit ofU.S. Provisional Application No. 61/422,667, filed on Dec. 14, 2010 and61/480,339, filed on Apr. 28, 2011, the contents of which are all herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

This specification relates to a location measurement.

BACKGROUND ART

Second generation (2G) mobile communication refers to transmission andreception of voice into digital and is represented by Code DivisionMultiple Access (CDMA), Global System for Mobile communication (GSM) andthe like. General Packet Radio Service (GPRS) was evolved from the GSM.The GPRS is a technology for providing a packet switched data servicebased on the GSP system.

Third Generation (3G) mobile communication refers to transmission andreception of image and data as well as voice (audio). Third GenerationPartnership Project (3GPP) has developed a mobile communication system(i.e., International Mobile Telecommunications (IMT-2000)), and adaptedWideband-CDMA (WCDMA) as Radio Access Technology (RAT). The IMT-200 and,the RAT, for example, the WCDMA are called as Universal MobileTelecommunication System (UMTS) in Europe. Here, UTRAN is anabbreviation of UMTS Terrestrial Radio Access Network.

Meanwhile, the third generation mobile communication is evolving to thefourth generation (4G) mobile communication.

As the 4G mobile communication technologies, a Long-Term EvolutionNetwork (LTE) whose standardization is being carried on in 3GPP and IEEE802.16 whose standardization is being carried on in IEEE have beenintroduced. The LTE uses a term ‘Evolved-UTRAN (E-UTRAN).’

The 4G mobile communication technology has employed Orthogonal FrequencyDivision Multiplexing (OFDM)/Orthogonal Frequency Division MultipleAccess (OFDMA). The OFDM uses a plurality of orthogonal subcarriers. TheOFDM uses an orthogonal property between Inverse Fast Fourier Transform(IFFT) and Fast Fourier Transform (FFT). A transmitter performs the IFFTfor data and transmits the data. A receiver performs the FFT for areceived signal to recover original data. The transmitter uses the IFFTfor concatenating a plurality of subcarriers, and the receiver uses thecorresponding FFT to segment the plurality of subcarriers.

Meanwhile, the 3G or 4G mobile communication system has a function partfor calculating the position (or location) of a terminal to provide alocation service that provides the location of the terminal.

Currently, there are several methods for calculating the location of theterminal, including a cell-ID method for transferring an ID of a cell towhich a mobile terminal belongs, a method for calculating the locationof a terminal through triangulation by measuring time taken for radiosignals to reach each base station from the terminal, and a method ofusing a satellite.

In the cell ID based (i.e. cell coverage) method, a position of an UE isestimated with the knowledge of its serving base station (i.e., aserving Node B). The information about the serving Node B and cell maybe obtained during a paging procedure, a locating area update procedure,a cell update procedure, an URA update procedure, or a routing areaupdate procedure

The cell coverage based positioning information can be indicated as theCell Identity of the used cell, the Service Area Identity or as thegeographical co-ordinates of a position related to the serving cell. Theposition information includes a QoS estimate (e.g. regarding achievedaccuracy) and, if available, the positioning method for the list of themethods) used to obtain the position estimate.

When geographical co-ordinates are used as the position information, theestimated position of the UE can be a fixed geographical position withinthe serving cell (e.g. position of the serving Node B), the geographicalcentre of the serving cell coverage area, or some other fixed positionwithin the cell coverage area. The geographical position can also beobtained by combining information on the cell specific fixedgeographical position with some other available information, such as thesignal RTT in FDD or Rx Timing deviation measurement and knowledge ofthe UE timing advance, in TDD.

Meanwhile, for the method of using the satellite, UE has to be equippedwith radio receivers capable of receiving GNSS signals. Indeed, examplesof GNSS include a GPS (Global Positioning System) and Galileo. In thisconcept, different GNSS (e.g. GPS, Galileo) can be used separately or incombination to perform the location of a UE.

Also, the method using a triangulation technique may be divided into twotype techniques. The one is a U-TDOA positioning method and the anotheris an OTDOA-IPDL (observed time difference of arrival with networkadjustable idle periods in down link) method.

First, The U-TDOA positioning method is based in network measurements ofthe Time Of Arrival (TOA) of a known signal sent from the FE andreceived at four or more LMUs. The method requires LMUs in thegeographic vicinity of the UE to be positioned to accurately measure theTOA of the bursts. Since the geographical co-ordinates of themeasurement units are known, the FE position can be calculated viahyperbolic trilateration. This method will work with existing UE withoutany modification. In most cases the UEs deeply inside the cell coverageradius does not need to receive signals from other cells. Only when theUE moves to cell coverage edge, it needs to listen to signals from othercells and possibly handover to other cells. This is contrary to the LElocation acquisition procedure, where the UE may need to listen to morethan 1 cell regardless of UE geographical position.

Second, The OTDOA-IPDL (observed time difference of arrival with networkadjustable idle periods in down link) method involves measurements madeby the UE of the frame timing (e.g. system frame number ? to systemframe number observed time difference)

FIG. 1

FIG. 1 illustrates an exemplary OTDOA method.

Referring FIG. 1, the OTDOA-IPDL (observed time difference of arrivalwith network adjustable idle periods in down link) method involvesmeasurements made by the UE of the frame timing (e.g. system framenumber ? to system frame number observed time difference). Thesemeasures are used in the network and the position of the UE iscalculated. The simplest case of OTDOA-IPDL is without idle periods. Inthis case the method can be referred to as simply OTDOA. The Node B mayprovide idle periods in the downlink, in order to potentially improvethe hearability of neighboring Node Bs. The support of these idleperiods in the UE is optional.

As such, in the OTDOA technique, the UE has to measure the timingdifference. But, if bandwidths allocated by each cell are different eachother, the UE suffers from measuring the timing difference.

DISCLOSURE OF INVENTION Solution to Problem

Therefore, an aspect of this specification is to address such drawbacks.That is, an aspect of this specification is to provide a solution forsolving the problem that bandwidths allocated by each cell are differenteach other.

In more detail, the solution may be to allow the UE to measure thetiming difference in a situation where bandwidths allocated by each cellare different each other. Also, the solution may be to allow each cellto sync it's bandwidth with other cell.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a method for measuring a location. The methodcomprises: receiving, by a User Equipment (UE) and from a serving cell,information on a bandwidth allocated for a positioning reference signal(PRS); receiving, by the User Equipment (UE) and from at least one ormore neighbor cells, information on a bandwidth allocated for a PRS;determining whether there is a difference between the bandwidths; andmeasuring, by the UE and based on a result of the determination a timingdifference between PRSs transmitted from the serving cell and the atleast one or more neighbor cells.

The bandwidths may have a relationship based on intra-frequency.

The measurement may include: If there is the difference, selecting thebiggest bandwidth among the bandwidths; setting, based on the biggestbandwidth, at least one parameter for measuring the timing differencebetween PRSs; and measuring the timing difference between PRSs accordingto the parameter. Here, The parameter includes at least one of: a firstparameter related to an accuracy with respect to the measurement; and asecond parameter related to the number of sub-frames available for themeasurement.

Alternatively, the measurement may include: If there is the difference,transmitting a request message for requesting a gap between the PRS ofthe first base station and the PRS of the neighbor base station.

During the gap, the UE may not receive any data from the first station.

Alternatively, the measurement may include: If there is the difference,selecting the smallest bandwidth among the bandwidths; setting, based onthe smallest bandwidth, at least one parameter for measuring the timingdifference between PRSs; and measuring the timing difference betweenPRSs according to the parameter.

Preferably, n the selection step, if the first base station is not areference cell, the smallest bandwidth may be selected.

The measurement may further include: transmitting information on the setparameter to the first base station.

To achieve those aspects of this specification, there is provided amethod for measuring a location performed by a first base station. Themethod may include: receiving, by the first base station and from atleast one or more neighbor base stations, information on a bandwidthallocated for a positioning reference signal of the neighbor basestation; determining whether there is a difference between the bandwidthof the neighbor base station and a bandwidth allocated for a PRS of thefirst base station; and if there is a difference, performing a proceduresuch that the bandwidths are equal each other.

The procedure may include transmitting a control signal for requestingthe neighbor base station to adjust the bandwidth thereby to be equal tothe bandwidth of the first base station.

Alternatively, the procedure may include adjusting the bandwidth of thefirst base station thereby to be equal to the bandwidth of the neighborbase station.

To achieve those aspects of this specification, there is provided a UserEquipment. The UE may comprise: a transceiver configured to receive,from a serving cell, information on a bandwidth allocated for apositioning reference signal (PRS) and receive, from at least one ormore neighbor cells, information on a bandwidth allocated for a PRS; anda controller configured to determine whether there is a differencebetween the bandwidths and control the transceiver to measure, based ona result of the determination, a timing difference between PRSstransmitted from the serving cell and the at least one or more neighborcells.

To achieve those aspects of this specification, there is provided a basestation. The base station may comprise a transceiver configured toreceive, from at least one or more neighbor base stations, informationon a bandwidth allocated for a positioning reference signal of theneighbor base station; and a controller cooperating with the transceiverand configured to determine whether there is a difference between thebandwidth of the neighbor base station and a bandwidth allocated for aPRS of the first base station, If there is a difference, the controllerperforms a procedure such that the bandwidths are equal each other.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an exemplary OTDOA method;

FIG. 2 illustrates one example scenario for detection of positioning RSin OTDOA method;

FIG. 3 illustrates one example of a propagation delay from cell A and B;

FIG. 4 illustrates one example of relative transmission time differencebetween two cells;

FIG. 5 illustrates one example of necessity of 3 sub-frame to preventinterference from serving cell.

FIG. 6 illustrates one exemplary location transfer procedure;

FIG. 7 illustrates a RSTD reporting time requirement in an FDD mode;

FIG. 8 illustrates one example of a case where a bandwidth allocated bythe serving cell is different from bandwidths allocated by at least oneor more neighbor cells;

FIG. 9 illustrates a first embodiment of the present invention in whichthe longest BW the serving cell and the neighboring cells is consideredto measure the PRS;

FIG. 10 illustrates a second embodiment of the present invention inwhich a bandwidth of the first cell is adjusted thereby to be equal to abandwidth of the other cell;

FIG. 11 illustrates a third embodiment of the present invention;

FIG. 12 illustrates one example of a measurement gap according to thethird embodiment of the present invention

FIG. 13 illustrates a case where the serving cell is not defined as areference cell and the bandwidth allocated by the serving cell isgreater than the bandwidth allocated by the target cell;

FIG. 14 illustrates a problem to be occurred in a case where the servingcell is not defined as a reference cell and the bandwidth allocated bythe serving cell is smaller than the bandwidth allocated by the targetcell and a solution according to the fourth embodiment; and

FIG. 15 is a configuration block diagram illustrating the UE 100 and abase station 200 according to the present invention.

MODE FOR THE INVENTION

This specification is applied, but not limited, to a measurementtechnique of the User Equipment's location. This specification may beapplicable to any communication system and method to which the technicalscope of this specification can be applied.

Technical terms used in this specification are used to merely illustratespecific embodiments, and should be understood that they are notintended to limit the present disclosure. As far as not being defineddifferently, all terms used herein including technical or scientificterms may have the same meaning as those generally understood by anordinary person skilled in the art to which the present disclosurebelongs to, and should not be construed in an excessively comprehensivemeaning or an excessively restricted meaning. In addition, if atechnical term used in the description of the present disclosure is anerroneous term that fails to clearly express the idea of the presentdisclosure, it should be replaced by a technical term that can beproperly understood by the skilled person in the art. In addition,general terms used in the description of the present disclosure shouldbe construed according to definitions in dictionaries or according, toits front or rear context, and should not be construed to have anexcessively restrained meaning.

A singular representation may include a plural representation as far asit represents a definitely different, meaning from the context. Terms‘include’ or ‘has’ used herein should be understood that they areintended to indicate an existence of several components or severalsteps, disclosed in the specification, and it may also be understoodthat part of the components or steps may not be included or additionalcomponents or steps may further be included.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure.

It will be understood that when an element is referred to as being“connected with” another element, the element can be directly connectedwith the other element or intervening elements may also be present. Incontrast, when an element is referred to as being “directly connectedwith” another element, there are no intervening elements present.

Embodiments of the present invention will be described below in detailwith reference to the accompanying drawings where those components arerendered the same reference number that are the same or are incorrespondence, regardless of the figure number, and redundantexplanations are omitted. In describing the present invention, if adetailed explanation for a related known function or construction isconsidered to unnecessarily divert the gist of the present invention,such explanation has been omitted but would be understood by thoseskilled in the art. The accompanying drawings are used to help easilyunderstood the technical idea of the present invention and it should beunderstood that the idea of the present invention is not limited by theaccompanying drawings. The idea of the present invention should beconstrued to extend to any alterations, equivalents and substitutesbesides the accompanying drawings.

The term ‘terminal’ is used herein, but the terminal may be replacedwith other terms, such as User Equipment (UE), Mobile Equipment (ME),Mobile Station (MS) and the like. Also, the terminal may be a type ofportable equipment, such as a cellular phone, PDA, a smart phone, anotebook and the like, or a type of fixed equipment, such as PC,vehicle-mounted device and the like.

Before description of the present invention with reference to theaccompanying drawings, the techniques explained in the specification althe present invention will be briefly described to help understanding ofthe present invention.

One example embodiment of the present invention uses a 3GPP standardbased OTDOA technique in which a user equipment (UE) receivespositioning reference signals (PRSs) transmitted from plural cells usingthe same E-UTRA Absolute Radio Frequency Channel Number (EARFCN) and theUE measures a Reference Signal Timing difference (RSTD). As such, theone example embodiment of the present invention provides a technique forincreasing an accuracy of the measurement of RSTD.

Requirements of the accuracy are defined in 3GPP standard documentTS36.133. In more detail, the documents describes that the measurementsatisfies the accuracy according to a transmission bandwidth allocatedfor the PRS by a neighbor cell. Here, a bandwidth allocated for achannel of PRS is independent from a bandwidth in which the PRS itselfis transmitted. Accordingly, after acquiring information on thebandwidth allocated for the channel of PRS by the target neighbor cell,the UE receives the PRSs during the channel, calculates the RSTD betweena PRS from a serving cell and a PRS from a target neighbor cell and thentransmits information the calculated RSTD.

But, the standard document ideally assumes that the serving cell and theneighbor cell allocate the same bandwidth for the PRS. But, thebandwidth allocated by the serving cell may be different from thebandwidth allocated by the neighbor cell. In this case, since the UEmerely considers only the bandwidth of the serving cell, but does notconsider the bandwidth of the neighbor cell using the same EARFCNtransmit, the accuracy is degraded and it is hard to satisfy therequirement.

Therefore, the one example embodiment of the present invention providesa solution to satisfy the accuracy of the measurement even when thebandwidths are different each other.

Now, the exemplary embodiments of the present invention will now bedescribed in detail with reference to the accompanying drawings.

FIG. 2 & FIG. 3

FIG. 2 illustrates one example scenario for detection of positioning RSin OTDOA method. And, FIG. 3 illustrates one example of a propagationdelay from cell A and B.

Assuming the UE is trying to receive certain signals from a target cell,when the UE is connected to a serving cell, there can be two possiblescenarios.

Referring FIG. 2(a), the first scenario is where the pathloss of thesignal from cell A, which is the serving (anchor) cell is smaller thanthe pathloss of the signal from cell B, which is the target cell.

Referring FIG. 2(b), the second scenario is where the pathloss of thesignal from cell A is similar to the pathloss of the signal from cell B.

In the second scenario the received signal from both cell are beingreceived at the UE in similar amplitudes and if the reception of thesignal to be measured from cell B has enough energy than the UE candetect the signal and take needed measurements.

In the first scenario the received signal from cell B will come into theUE much smaller compared to signal received front cell A. In the UEsignal amplifying chain called the Automatic Gain Control (AGC) willamplify the received total signal to be fitted into the dynamic range ofthe Analog to Digital Converter (ADC). If the received signal from cellA is larger than the signal from cell B, than the received total signalwill be in fact similar to signal from cell A. Since the AGC only takesinto account the total received signal when adjusting the amplifiergains, it might be possible that the received signal from cell B to belost within the quantization errors in the ADC. So in the first scenariono matter how well the measurement signal sequence was designed, itwould be very likely that the UE cannot detect the signal sequence fromcell B.

To overcome possible scenarios such as the first scenario mentioned, theserving cell can configure idle periods or signal non-transmittingdurations. This will effectively kill the signal from cell A and allowthe AGC to adapt to the signal source from cell B thus allowing adequateADC for received signal from cell B.

When signal is being transmitted through space (air), there is signalpropagation delays involved. For example even if two signals aretransmitted in the same time instant depending on the position of thesignal reception the signals from two different transmission points canbe received in different times. This is depicted as an example in FIG.3, where the UE is located further away from Cell B than Cell A.

So regardless of whether or not the deployed cells are synchronized, thesignals from different cells can be received at different timings. For asystem which targets the maximum cell radius as 100 km, the maximumpropagation delay which could occur from the UE side would beapproximately 100 [km]/300000 [km/s]s=0.334 ms (micro seconds). Forsynchronously deployed cells the maximum signal deviation would be±0.334 ms at the receiver side. For asynchronously deployed cells thetransmission signal at the eNB may already be out of synchronization.From the subframe point of view the maximum deviance between two cellsis ±0.5 ms (or half of a subframe). This is because if the subframetiming differences between 2 cells relative to two distinct referencesubframe are larger than 0.5 ms, than the reference subframe could beredefined so that the relative time difference is always smaller orequal to ±0.5 ms. Of course this is assuming that the subframe length isequal to 1 ms and that all transmissions and measurements are done bysubframe by subframe basis.

FIG. 4 & FIG. 5

FIG. 4 illustrates one example of relative transmission time differencebetween two cells. FIG. 5 illustrates one example of necessity of 3sub-frame to prevent interference from serving cell.

FIG. 4(a) shows the relative transmission time difference between twocells to be 0 ms. FIG. 4(b) shows the relative transmission timedifference between two cells to be 0.5 ms. FIG. 4(b) shows the relativetransmission time difference between two cells to be 0.75 ms, but from adifferent perspective this would result in negative 0.25 ms timedifference.

For an any given serving cell to receive signal from a given target cellmaximum 3 sub-frames would be need to be idled in order to receive thesignal from a certain target cell without any interference from theserving cell.

So depending on the measurement signal transmission timing of the targetcell and the idle subframe timing of the serving cell, there would beneed to configure consecutive 1, 2, or 3 idle sub-frames.

So we can configure the network to have consecutive 1, 2 (or 3) idlesubframe in the system, depending on the timing relationship between theserving cell and the measurement target cell(s). It can also possiblefor the UE to report the measured signal delay relative to the start ofserving cell first idle subframe. This would allow the eNB a systematicway of calculating relative delay of the measured signal and limit thesignal delay measurement to be within maximum of 3 ms.

In order for the UE take measurement without reading the subframeboundary or the radio frame boundary of the target cell, the servingcell can inform the UE of the target cell ID and approximate measurementsubframe timing given in terms of subframe number and system framenumber of the serving cell. Additionally the serving cell can inform theUE of the measurement signal bandwidth and frequency location of themeasurement signal of the target cell. This would allow the UE to ableto blindly detect the measurement signal without any target cellsearching and target cell synchronization procedures.

The information needed to take measurement from the target cell can bebroadcasted by the serving cell. This includes the actual target cellIDs. This is possible because the network is already geographicallyaware of the exact position of the eNBs. This enables the serving cellto be aware of the nearest cells around it, and also allows eliminationof cells which do not contribute to delay measurement enhances such ascells with Tx antennas which are co-located with the serving cell (i.e.3 sectors within the eNB).

FIG. 6

FIG. 6 illustrates one exemplary location transfer procedure.

Referring to FIG. 6, the location information transfer procedure isshown.

1) First, the server sends a Request Location Information message to thetarget to request location information, indicating the type of locationinformation needed and potentially the associated QoS.

2) The target sends a Provide Location Information message to the serverto transfer location information. The location information transferredshould match or be a subset of the location information requested instep 1 unless the server explicitly allows additional locationinformation. This message may carry an end transaction indication.

3) The target sends additional Provide Location Information messages tothe server to transfer location information. The location informationtransferred should match or be a subset of the location informationrequested in step 1 unless the server explicitly allows additionallocation information. The last message carries an end transactionindication.

Meanwhile, OTDOA-Neighbour Cell Info List can be sent by the network inorder to facilitate measurement of PRS for other cells.

The IE OTDOA-Neighbour Cell Info List is used by the location server toprovide neighbor cell information for OTDOA assistance data. TheOTDOA-Neighbour Cell Info List is sorted according to best measurementgeometry at the a priori location estimate of the target device. I.e.,the target device is expected to provide measurements in increasingneighbor cell list order (to the extent that this information isavailable to the target device).

The Table 1 shows conditional presence of Neighbor cell informationelements in ASN.1

TABLE 1 Conditional presence Explanation NotsameAsRef0 The field ismandatory present if the ARFCN is not the same as for the referencecell; otherwise it is not present. ARFCN is the carrier frequency valueof the cell. NotsameAsRef1 The field is mandatory present if the cyclicprefix length is not the same as for the reference cell; otherwise it isnot present. NotsameAsRef2 The field is mandatory present if the PRSconfiguration is not the same as for the reference cell; otherwise it isnot present. NotsameAsRef3 The field is mandatory present if the antennaport configuration is not the same as for the reference cell; otherwiseit is not present. NotsameAsRef4 The field is mandatory present if theslot timing is not the same as for the reference cell; otherwise it isnot present. InterFreq The field is optionally present, need OP, if theARFCN is not the same as for the reference cell; otherwise it is notpresent.

Also, the Table 2 Shows OTDOA-Neighbor cell Information list fielddescriptions.

TABLE 2 OTDOA-NeighbourCellInfoList field descriptions physCellId Thisfield specifies the physical cell identity of the neighbor cellcellGlobalId This field specifies the ECGI, the globally unique identityof a cell in E-UTRA, of the neighbor cell, as defined in [12]. Theserver provides this field if it considers that it is needed to resolveany ambiguity in the cell identified by physCellId. Earfcn This fieldspecifies the ARFCN of the neighbor cell. cpLength This field specifiesthe cyclic prefix length of the neighbor cell PRS. prsInfo This fieldspecifies the PRS configuration of the neighbor cell. antennaPortConfigThis field specifies whether 1 (or 2) antenna port(s) or 4 antenna portsfor cell specific reference signals are used. slotNumberOffset Thisfield specifies the slot number offset between this cell and thereference cell. The offset corresponds to the number of full slotscounted from the beginning of a radio frame of the reference cell to thebeginning of the closest subsequent radio frame of this cell. The offsetis used to determine the neighbor cell slot number which is used forgeneration of reference signal sequence as defined in [16]. If thisfield is absent, the slot timing is the same as for the reference cell.prs-SubframeOffset This field specifies the offset between the first PRSsubframe in the reference cell on the reference carrier frequency layerand the first PRS subframe in the closest subsequent PRS burst of theother cell on the other carrier frequency layer. The value is given innumber of full sub-frames. If the ARFCN is not the same as for thereference cell and the field is not present, the receiver shall considerthe PRS subframe offset for this cell to be 0. expectedRSTD This fieldindicates the RSTD value that the target device is expected to measurebetween this cell and the reference cell in OTDOAReferenceCellInfo. TheRSTD value can be negative and is calculated as (expectedRSTD-8192). Theresolution is 3 T_(s), with T_(s), = 1/(15000*2048) seconds.expectedRSTD-Uncertainty This field indicates the uncertainty inexpectedRSTD value. The uncertainty is related to the location serversa-priori estimation of the target device location. TheexpectedRSTDUncertainty defines the following search window for thetarget device: [expectedRSTD? expectedRSTD- Uncertainty] < measuredRSTD< [expectedRSTD ??expectedRSTD- Uncertainty]The scale factor of theexpectedRSTD-Uncertainty field is 3 T_(s), with T_(s) = 1/(15000*2048)seconds.

Meanwhile, configuration of Positioning RS (PRS) will be explainedbelow.

The cell specific sub-frame configuration period T_(PRS) and the cellspecific sub-frame offset Δ_(PRS) for the transmission of positioningreference signals are listed in Table 3 below. The PRS configurationindex I_(PRS) is configured by higher layers. Positioning ReferenceSignals (PRSs) are transmitted only in configured DL sub-frames. PRSsare transmitted in special sub-frames. PRSs are transmitted in N_(PRS)consecutive downlink sub-frames, where N_(PRS) is configured by higherlayers.

The positioning reference signal instances, for the first sub-frame ofthe N_(PRS) downlink sub-frames, satisfy (10×n_(t)+└n_(s)/2┘−Δ_(PRS))modT_(PRS)=0.

Table 3 shows sub-frame configuration of the PRS.

TABLE 3 PRS periodicity T_(PRS) (sub-frames) [160]  [320]  [640]  [1280][Reserved]

Meanwhile, measurements of Positioning RS will be explained below.

When the physical layer cell identities of neighbor cells together withthe OTDOA assistance data are provided, the UE is able to detect andmeasure intra-frequency RSTD, specified in 3GPP TS 36.214, for at leastn=16 cells, including the reference cell, on the same carrier frequencyf1 as that of the reference cell within T_(RSTD) ms as given below:(T _(RSTD) =T _(RSTD)·(M−1)+Δms,

where T_(RSTD) is the total time for detecting and measuring at least ncells, T_(PRS) is the cell-specific positioning sub-frame configurationperiod as defined in 3GPP TS 36.211, M is the number of PRS positioningoccasions as defined in Table below, where each PRS positioning occasioncomprises of N_(PRS) (1≤N_(PRS)≤6) consecutive downlink positioningsub-frames defined in 3GPP TS 36.211, and

$\Delta = {{160 \cdot \left\lceil \frac{n}{M} \right\rceil}{ms}}$is the measurement time for a single PRS positioning occasion whichincludes the sampling time and the processing time.

Table 4 shows number of PRS positioning occasions within T_(RSTD)

TABLE 4 Positioning sub-frame configuration period T_(PRS) 160 ms >160ms

The UE physical layer is capable of reporting RSTD for the referencecell and all the neighbor cells i out of at least (n−1) neighbor cellswithin provided:

(PRSÊ_(s)/Iot)_(ref≥−6 dB) for all Frequency Bands for the referencecell,

(PRSÊ_(r)/Iot)_(i≥−13 dB) for all Frequency Bands for neighbour cell i,

(PRSÊ₅/Iot)_(ref) and (PRSÊ₈/Iot)_(l) conditions apply for allsub-frames of at least L=M/2 PRS positioning occasions,

PRP 1.2|dBm≥−127 dBm for Frequency Bands 1, 4, 6, 10, 11, 18, 19, 21,

PRP 1,2|dBm≥−126 dBm for Frequency Bands 9,

PRP 1,2|dBm≥−125 dBm for Frequency Bands 2, 5, 7,

PRP 1,2|dBm≥−124 dBm for Frequency Bands 3, 8, 12, 13, 14, 17, 20.

PRSÊ_(s)/Iot is defined as the ratio of the average received energy perPRS RE during the useful part of the symbol to the average receivedpower spectral density of the total noise and interference for this RE,where the ratio is measured over all REs which carry PRS.

The time T_(RSTD) starts from the first sub-frame of the PRS positioningoccasion closest in time after the OTDOA assistance data in theOTDOA-ProvideAssistanceData message as specified in 3GPP TS 36.355, isdelivered to the physical layer of the UE as illustrated in figurebelow.

The RSTD measurement accuracy for all measured neighbor cells i shall befulfilled according to the accuracy requirements.

FIG. 7

FIG. 7 illustrates a RSTD reporting time requirement in an FDD mode.

As shown in FIG. 7, the measurement report is not delayed by other LPPsignaling on the DCCH. This measurement reporting delay excludes a delayuncertainty resulted when inserting the measurement report to the TTI ofthe uplink DCCH. The delay uncertainty is: 2×TTIDCCH. This measurementreporting delay excludes any delay caused by no UL resources for UE tosend the measurement report.

Table 5 shows a reference signal time difference (RSTD)

TABLE 5 Definition The relative timing difference between cell j andcell i, defined as T_(Sub-frameRxj) T_(Sub-frameRxi), where:T_(Sub-frameRxj) is the time when the UE receives the start of onesub-frame from cell j T_(Sub-frameRxi) is the time when the UE receivesthe corresponding start of one sub-frame from cell i that is closest intime to the sub-frame received from cell j. The reference point for theobserved sub-frame time difference shall be the antenna connector of theUE. Applicable RRC_CONNECTED intra-frequencyRRC_CONNECTED forinter-frequency

The Table 6 shows accuracies required for the RSTD measurement performedby the UE, according to the bandwidth allocated for PRS by the neighborcell. The accuracies in Table 6 are valid under the followingconditions:

Conditions defined in 36.101 Section 7.3 for reference sensitivity arefulfilled.

PRP 1,2|dBm≥−127 dBm for Bands 1, 4, 6, 10, 11, 18, 19, 21, 33, 34, 35,36, 37, 38, 39, 40,

PRP 1,2|dBm≥−126 dBm for Band 9,

PRP 1,2|dBm≥−125 dBm for Bands 2, 5, 7,

PRP 1,2|dBm≥−124 dBm for Bands 3, 8, 12, 13, 14, 17, 20.

There are no measurement gaps overlapping with the PRS sub-frames of themeasured cell.

The parameter expectedRSTDUncertainty signaled over LPP by E-SMLC asdefined in 3GPP TS 36.355 is less than 5 μs.

TABLE 6 Conditions Bands 1, 4, 6, 10, 11, 18, 19, PRS Number of 21, 33,34, 35, Bands Transmission Sub-frames 36, 37, 38, 39 Bands 3, 8, 12,Band Bandwidth Available for Accuracy &40 2, 5, 7, 17 13, 14, 20 9Parameter [RB] Measurements Unit [Ts] lo lo lo lo RSTD for 6, 15   6T_(s) ±15  −121 −119 −118 −120 (PRS 25 ≥2 ±6 dBm/15 kHz dBm/15 kHzdBm/15 kHz dBm/15 kHz Ês/lot)_(ref) ≥ 50, 75, 100 ≥1 ±5 . . . . . . . .. . . . −6 dB and  −50  −50  −50  −50 (PRS dBm/BW_(Channel)dBm/BW_(Channel) dBm/BW_(Channel) dBm/BW_(Channel) Ês/lot); ≥ −13 dBNote 1: lo is assumed to have constant EPRE across the bandwidth. Note2: Ts is the basic timing unit defined in 3GPP TS 36.211.

The Table 7 shows a relationship between a bandwidth and a number ofresource blocks (RBs).

TABLE 7 Bandwidth [MHz] 1.4 3 5 10 15 20 RB 6 15 25 50 75 100

FIG. 8

FIG. 8 illustrates one example of a case where a bandwidth allocated bythe serving cell is different from bandwidths allocated by at least oneor more neighbor cells.

Referring to FIG. 8(a), if a UE which belongs to a serving cell havingallocated a 3 MHz bandwidth tries to receive a PRS from a target cellhaving allocated a 10 Mhz bandwidth for the PRS, the accuracy of themeasurement is changed from ±15 Ts to ±5 Ts. In other words, theaccuracy will be very tight.

Referring to FIG. 8(b), if the bandwidth allocated for the PRS by theserving cell greater than the bandwidth allocated for the PRS by theneighbor cell, when the UE tries to receive the PRS from the neighborcell, the UE could receive an unwanted interference via the bandwidth ofthe serving cell greater than the bandwidth of the neighbor cell. Suchthe interference sometimes causes the accuracy to be degraded.

Therefore, hereinafter, techniques to satisfy the requirement of theaccuracy for measuring RSTD between neighbor cells, which have arelationship based on intra-frequency, will be described

FIG. 9 to FIG. 11 illustrates three embodiments of the present inventionto increase the accuracy.

FIG. 9

FIG. 9 illustrates a first embodiment of the present invention in whichthe longest BW in the serving cell and the neighboring cells isconsidered to measure the PRS.

Referring to FIG. 9, the first embodiment allows the FE to measure aReference Signal Timing difference (RSTD) by using information on abandwidth allocated for the PRS by at least one neighbor cell, if thebandwidth allocated for the PRS by the neighbor cell is greater than abandwidth allocated for the PRS by a serving cell.

Generally, an accuracy of the measurement is varied dependent on abandwidth allocated for the PRS. And, the greater is the bandwidthallocate for the PRS, the greater is the frequency sample rate therebyto acquire an excellent accuracy of the measurement.

The UE can obtain information on the bandwidths allocated for PRS by atleast one neighbor cells by receiving an RRC signal message. Therefore,the UE can select at least one cell having the greatest bandwidth amongthe serving cell at least one neighbor cell. And the UE considers theselected cell as a reference cell. And, the UE sets, based on thebiggest bandwidth, at least one parameter for measuring the timingdifference between PRSs. The parameter includes at least one of a firstparameter related to an accuracy with respect to the measurement, and asecond parameter related to the number of sub-frames available for themeasurement. And then the UE measures the RSTD between PRSs transmittedfrom the serving cell and the neighbor cell according to the setparameter.

In other words, as shown in FIG. 9, the UE does not consider the servingcell as a reference cell, if a bandwidth of the serving cell is not agreatest. Rather, as shown in FIG. 9, the UE measures the PRS accordingto the greatest bandwidth allocated for PRS thereby to obtain anexcellent accuracy.

However, if the UE tries to receive PRSs from the serving cell and theneighbor cell which allocates a smaller bandwidth than the greatestbandwidth, an interference signal may also be received by the UE. But,since the UE already acquires information on bandwidth allocated by eachcell, the UE can minimize the interference signal by using a digitalfilter.

As described until now, the first embodiment makes it possible tosatisfy the requirement for the accuracy of the measurement.

FIG. 10

FIG. 10 illustrates a second embodiment of the present invention inwhich a bandwidth of the first cell is adjusted thereby to be equal to abandwidth of the other cell.

Referring to FIG. 10, the e second embodiment allows the serving celland the neighbor cell to allocate the same bandwidth for the PRS. To dothis, the serving cell may exchanges information on the bandwidthallocated for the PRS with the neighbor cells. After receiving theinformation, each neighbor cell adjusts an allocation of the bandwidth.

In more detail, the serving cell and the neighbor cell exchanges theinformation via an X2 interface. Alternatively, an operator may requestthe serving cell and the neighbor cell to allocate the same bandwidth byusing a Operation & Management (O&M) protocol.

FIG. 11 & FIG. 12

FIG. 11 illustrates a third embodiment of the present invention. And,FIG. 12 illustrates one example of a measurement gap according to thethird embodiment of the present invention

Referring to FIG. 11, the third embodiment allows the UE to sequentiallyreceive a plurality of PRSs.

In more detail, if a bandwidth allocated for a PRS received from onecell is smaller or greater than the bandwidth allocated by the servingcell, the UE has to tune a RF component in order to receive acorresponding PRS in each bandwidth. But such tuning requires a time.Therefore, the serving cell provides a time gap to the UE such that theUE has a enough time to tune it's RF component. To do this, the servingcell can not transmit any signals when the UE has to receive acorresponding PRS from each neighbor cell.

For this, the UE transmits a request message for requesting a gap to theserving cell. The request message includes information on bandwidthsallocated by at least one neighbor cell.

Meanwhile, the UE adaptively or actively controls it's filter in orderto receive a PRS in a corresponding bandwidth allocated by each cellsuch that the UE can measures a RSTD between PRSs having a relationshipbased on intra-frequency.

Table 7 shows a pattern of the gap for the measurement. This gap is alsoused to monitor inter-frequency EARFCN and inter-RAT system. The gapsupports 40 ms and 80 ms. Also, a measurement period may be 6 ms.

TABLE 8 Minimum available time for inter-frequeney Measurement andinter-RAT Gap measurements Gap Measurement Repetition during 480 msPattern Gap Length Period period(Tinter1, Measurement Id (MGL, ms)(MGRP, ms) ms) Purpose 0 6 40 60 Inter-Frequency E-UTRAN FDD and TDD,UTRAN FDD, GERAN, LCR TDD, HRPD, CDMA2000 1× 1 6 80 30 Inter-FrequencyE-UTRAN FDD and TDD. UTRAN FDD, GERAN, LCR TDD, HRPD, CDMA2000 1×

In actual, in order to measure RSTD between PRSs, it is required to setthe measurement gap in a physical layer, And, if the measurement gap isset, the measurement is performed in an optimal way. Referring to FIG.12, the measurement gap exists between sub-frames in which the servingcell has to transmit data.

FIG. 13 & FIG. 14

FIG. 13 illustrates a case where the serving cell is not defined as areference cell and the bandwidth allocated by the serving cell isgreater than the bandwidth allocated by the target cell. And, FIG. 14illustrates a problem to be occurred in a case where the serving cell isnot defined as a reference cell and the bandwidth allocated by theserving cell is smaller than the bandwidth allocated by the target celland a solution according to the fourth embodiment.

Referring FIG. 13, the serving cell allocates a 5 MHz bandwidth for thePRS and a neighbor cell which is defined as a reference cell allocates a15 MHz bandwidth, and also a target cell allocates a 3 MHz bandwidth.Here, referring to Table 7, 3 MHz corresponds to a 15 RBs, 5 MHzcorresponds to a 25 RBs, and 15 MHz corresponds to a 75 RBs. Also,referring to Table 6, if the bandwidth is 15 RBs, the number ofsub-frames required for the measurement is 6. And, if the bandwidth is25 RBs, the number of sub-frames is 2. And also, if the bandwidth is 75RBs, the number of sub-frames is 1.

Therefore, the PRS transmitted from the serving cell is measured during2 sub-frames (or 2 TTI). And, the PRS transmitted from the referencecell is measured during 1 sub-frame. And also, the PRS transmitted fromthe target cell is measured during 1 sub-frame.

Meanwhile, if the UE uses a filter to be tuned for the 5 MHz bandwidthof the serving cell, determines the number of sub-frames based on thesmaller one from among the bandwidth of the target cell and thebandwidth of the reference cell (in other words, the UE selects 6sub-frames), and measures the RSTD between the PRSs transmitted from theserving cell and the target cell in reference to the PRS transmittedfrom the reference cell during the determined number of sub-frames, thenthere is no problem, since the measurement is performed during the 6sub-frames which are enough long time to receive the PRS transmittedfrom the serving cell and since the filter is tuned for the 5 MHzgreater than the 3 MHz of the target cell.

However, referring to FIG. 14(a), the serving cell is not defined as areference cell and the bandwidth allocated by the serving cell issmaller than the bandwidth allocated by the target cell.

In such a case, if the UE uses a filter to be tuned for the 3 MHzbandwidth of the serving cell, selects the number of sub-frames based onthe smaller one from among the bandwidth of the reference cell and thebandwidth of the target cell (in other words, the UE selects 2sub-frames), and measures the RSTD between the PRSs transmitted from theserving cell and the target cell based on the PRS transmitted from thereference cell during the determined number of sub-frames, then there isa problem, since the measurement performed during only the 2 sub-framesis not sufficient to satisfy the accuracy in a condition where thefilter is tuned for the 3 MHz smaller than the 5 MHz of the target cell.In other words, since the PRS on 5 MHz transmitted from the target cellpasses through the filter tuned for the 3 MHz, the original 2 sub-framesare not enough.

To solve this problem, FIG. 14(b) shows a solution according to thefourth embodiment. The fourth embodiment allows the UE to determine thenumber of sub-frames based on the smallest bandwidth in all the cellsincluding the serving cell, the reference cell and the target cell.

In more detail, FIG. 14(b) shows one example case where the serving cellallocates a 3 MHz bandwidth for the PRS and the target cell allocatesthe 5 MHz bandwidth.

In such a case, if the UE uses a filter to be tuned for the 3 MHzbandwidth of the serving cell, determines the number of sub-frames basedon the smallest bandwidth in all the cells including the serving cell,the reference cell and the target cell (in other words, the UE selects 6sub-frames), and measures the RSTD between the PRSs transmitted from theserving cell and the target cell based on the PRS transmitted from thereference cell during the determined number of sub-frames (i.e., during6 sub-frames), then there is no problem, since the measurement isperformed during the 6 sub-frames which are enough long time to receivethe PRS transmitted from the target cell although the filter is tunedfor the 3 MHz smaller than the 5 MHz of the target cell.

Meanwhile, according to the fourth embodiment, the UE transmitsinformation on a parameter related to the determined number of thesub-frames to the serving cell.

The method according to the present invention as described above may beimplemented by software, hardware, or a combination of both. Forexample, the method according to the present invention may be stored ina storage medium (e.g., internal memory, flash memory, hard disk, and soon), and may be implemented through codes or instructions in a softwareprogram that can be performed by a processor such as microprocessor,controller, micro controller, ASIC (application specific integratedcircuit), and the like. Hereinafter, it will be described with referenceto FIG. 11.

FIG. 15

FIG. 15 is a configuration block diagram illustrating the UE 100 and abase station 200 according to the present invention.

As illustrated in FIG. 15, the UE 100 may include a storage unit 101, atransceiver 103, and a controller 102. Also, the base station 200 mayinclude a storage unit 201, a transceiver 203, and a controller 202. Thebase station 200 may be the serving cell, the reference cell, or thetarget cell.

The storage units store a software program implementing the foregoingmethod as illustrated in FIGS. 1 through 14. Also, the storage unitsstore information within each of the received messages (or signals).

Each of the controllers controls the storage units and the transceivers,respectively. Specifically, the controllers implements the foregoingmethods, respectively, stored in each of the storage units.

The present invention has been explained with reference to theembodiments which are merely exemplary. It will be apparent to thoseskilled in the art that various modifications and equivalent otherembodiments can be made in the present invention without departing fromthe spirit or scope of the invention. Also, it will be understood thatthe present invention can be implemented by selectively combining theaforementioned embodiment(s) entirely or partially. Thus, it is intendedthat the present invention cover modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

What is claimed is:
 1. A method for performing, by a user equipment(UE), reference signal time different (RSTD) measurement, comprising:receiving, by the UE, a positioning reference signal (PRS) of a neighborcell and a PRS of a reference cell; and measuring, by the UE, a RSTDwith a RSTD measurement accuracy based on the PRSs of the neighbor andreference cells, wherein the RSTD is a relative timing differencebetween the neighbor cell and the reference cell, and wherein the RSTDmeasurement accuracy is determined based on a minimum PRS bandwidthwhich is minimum of a bandwidth of a serving cell, a bandwidth for thePRS of the neighbor cell and a bandwidth for a PRS of the referencecell.
 2. The method according to claim 1, further comprising: receiving,by the UE, observed time difference of arrival (OTDOA) assistance data,wherein the OTDOA assistance data includes information on the bandwidthfor the PRS of the neighbor cell and information on the bandwidth forthe PRS of the reference cell.
 3. The method according to claim 2,wherein the OTDOA assistance data further includes information on anumber of consecutive downlink subframes with the PRS of the neighborcell and information on a number of consecutive downlink subframes withthe PRS of the reference cell.
 4. The method according to claim 1,wherein the RSTD is measured in multiple downlink subframes, and whereina number of the multiple downlink subframes available for measuring theRSTD is associated with the minimum PRS bandwidth.
 5. The methodaccording to claim 1, wherein the reference cell is other than theserving cell.
 6. The method according to claim 1, further comprising:reporting, by the UE, the RSTD to a network for positioning of the UE.7. A user equipment (UE) for performing reference signal time different(RSTD) measurement, comprising: a transceiver, and a controllerconfigured to control the transceiver, configured to: control thetransceiver to receive a positioning reference signal (PRS) of aneighbor cell and a PRS of a reference cell; and measure a RSTD with aRSTD measurement accuracy based on the PRSs of the neighbor andreference cells, wherein the RSTD is a relative timing differencebetween the neighbor cell and the reference cell, and wherein the RSTDmeasurement accuracy is determined based on a minimum PRS bandwidthwhich is a minimum of a bandwidth of a serving cell, a bandwidth for thePRS of the neighbor cell and a bandwidth for a PRS of the referencecell.
 8. The UE according to claim 7, wherein the processor isconfigured to control the receiver to further receive observed timedifference of arrival (OTDOA) assistance data, and wherein the OTDOAassistance data includes information on the bandwidth for the PRS of theneighbor cell and information on the bandwidth for the PRS of thereference cell.
 9. The UE according to claim 8, wherein the OTDOAassistance data further includes information on a number of consecutivedownlink subframes with the PRS of the neighbor cell and information ona number of consecutive downlink subframes with the PRS of the referencecell.
 10. The UE according to claim 7, wherein the processor isconfigured to measure the RSTD in multiple downlink subframes, andwherein a number of the multiple downlink subframes available formeasuring the RSTD is associated with the minimum PRS bandwidth.
 11. TheUE according to claim 7, wherein the reference cell is other than theserving cell.
 12. The UE according to claim 7, wherein the processor isconfigured to control the RF unit to report the RSTD to a network forpositioning of the UE.